Do you mean steam or do you mean pneumatic? I’ve never heard of steam delivered mail but pneumatic was really popular. https://chicagology.com/chicagopostoffic

Do you mean steam or do you mean pneumatic? I’ve never heard of steam delivered mail but pneumatic was really popular. https://chicagology.com/chicagopostoffice/pneumatictubesystem/ https://chicagology.com/chicagopostoffice/pneumatictubesyste...